Acrylonitrile is industrially important as a material for synthetic resins, synthetic fibers, synthetic rubbers, etc., while acrylic acid is also industrially important as a material for highly water absorptive resins, synthetic resins, coating materials, adhesives, plasticizers, etc. Heretofore, acrylonitrile has been produced by reacting propylene with ammonia for gas phase catalytic oxidation, while acrylic acid has been produced by a two step gas phase catalytic oxidation reaction of propylene. Recently, an attention has been drawn to a method for production of an unsaturated nitrile wherein a more inexpensive alkane is used as a starting material. Particularly, from the difference in price between propylene and propane, an attention has been drawn to a method for production of acrylonitrile or acrylic acid wherein inexpensive propane is used as a starting material, and proposals for a catalyst and a process have been made. Among them, an interest has been drawn to development of a method for production of acrylonitrile by a so-called ammoxidation reaction method wherein propane is used as a starting material and reacted with ammonia and oxygen in a gas phase for catalytic oxidation in the presence of a catalyst.
With respect to the method for production of acrylonitrile by this ammoxidation of propane, methods have been proposed wherein as the catalyst, for example, a Mo--Bi--P type catalyst (JP-A-48-16887), a Mo--Cr--Te type catalyst (U.S. Pat. No. 5,171,876), a V--Sb type catalyst (JP-A-47-33783, JP-B-50-23016, JP-A-1-268668, JP-A-2-180637), a V--Sb--U--Ni type catalyst (JP-B-47-141371), or a V--Sb--W--P type catalyst (JP-A-2-95439) is used. Further, recently, a Mo--V--Te type catalyst (JP-A-2-257, JP-A-5-148212, JP-A-5-208136, JP-A-6-279351, JP-A-6-287146, JP-A-7-108101), or a Mo--V--Sb type catalyst (JP-A-9-157241), has been proposed as an effective catalyst.
Further, JP-A-3-27350 proposes a method wherein unreacted propane is separated and recovered from a gas discharged from a reactor and again used as a starting material gas for reaction, thereby increasing the yield of acrylonitrile from propane.
On the other hand, also in a method for production of an unsaturated carboxylic acid, an attention has been drawn to a method wherein a more inexpensive alkane is used as a starting material. Particularly, with respect to production of acrylic acid in one step by a gas phase catalytic oxidation reaction method wherein inexpensive propane is used as a starting material and subjected to catalytic oxidation with oxygen in a gas phase in the presence of a catalyst, a method has been proposed in which as a catalyst, a Bi--Mo--V type and/or divanadyl pyrophosphate catalyst (JP-A-3-170445, the 11th International Catalyst Meeting, Collection of Summaries, p.1205-1214) or a P--Mo--Sb--W type catalyst (Belgian Patent Application No. 9500449) is used. However, recently, it has been proposed that a Mo--V--Te type catalyst (JP-A-6-279351) can be used.
However, the above-mentioned production methods heretofore proposed, are directed to produce them separately by totally independent reaction apparatus, and not intended to produce both of them simultaneously. Of course, nothing is disclosed with respect to the reaction operation conditions for producing both.